Pulse generator for controlling the valves of an internal combustion engine

ABSTRACT

A pulse generator rotating synchronously with the crank shaft of the engine feeds pulses through a differentiator to a staircase generator of which the output is connected to the inverting inputs of four operational amplifiers acting as threshold switches, the outputs of which are connected to respective inputs of two bistable triggers of which the outputs are connected each to a switching amplifier that controls the inlet or outlet valve of one cylinder of the internal combustion engine. In one modification, the invention is adapted to a four cylinder engine.

United States Patent 1191 Schmidt et a1.

[ PULSE GENERATOR FOR CONTROLLING THE VALVES OF AN INTERNAL COMBUSTION ENGINE Inventors: Peter Schmidt, Schwieberdingen;

Lothar Raff, Hochberg, both of Germany Robert Bosch GmbH, Stuttgart, Germany Filed: Aug. 19, 1971 Appl. No.: 173,008

Assignee:

[30] Foreign Application Priority Data Jan. 15,1971 Germany P 2101 761.8

US. Cl l 23/90.12, 123/9014, 123/9015, 123/102, 123/148 E Int. Cl. F011 9/02, F011 9/04, F011 1/34 Field of Search 123/9012, 90.14, 123/90.l1, 90.15, 102, 148 E 101 H0O P2... 5

[ June 26, 1973 [56] References Cited UNITED STATES PATENTS 2,520,537 8/1950 Forman 123/9011 x 3,548,793 12/1970 Richardson 123/9015 x Primary Examiner-Al Lawrence Smith Att0rney-Michael S. Striker [5 7] ABSTRACT A pulse generator rotating synchronously with the crank shaft of the engine feeds pulses through a differentiator to a staircase generator of which the output is connected to the inverting inputs of four operational amplifiers acting as threshold switches, the outputs of which are connected to respective inputs of two bistable triggers of which the outputs are connected each to a switching amplifier that controls the inlet or outlet valve of one cylinder of the internal combustion engine. In one modification, the invention is adapted to a four cylinder engine.

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SHEET 7 0F 7 Q. I M478 ow I INVENTORS Peter SCHMIDT Lothor RAF F Bya: JAbv their ATTORNEY BACKGROUND OF THE INVENTION The invention relates to a pulse generator for operating the electrohydraulic or electropneumatic control for the inlet and outlet valves of an internal combustion engine.

With experimental internal combustion engines, the valves are electrohydraulically or electropneumatically controlled, with a view to increasing the torque at very high rpms by more quickly opening and closing the valves than is possible with mechanical valve control operated by the cam shaft. The average of the crosssectional area of the opening over the whole of the open time of the valve can be enlarged, and more fuel can be supplied to the cylinder.

It has been attempted to produce the valve control pulses with an electric distributor. Since in some circumstances the control pulses for the inlet and outlet valves must overlap even with a single cylinder, an engine having two or more cylinders requires a distributor having a plurality of switching decks. These distributors have the further widely recognized disadvantages of contact bounce, chatter, and burn associated with mechanical switches. When using electrohydraulically and electropneumatically controlled valves for experimental and high power engines, there is the additional requirement that the opening time and the length of opening of the valves must beadjustable.

SUMMARY OF THE INVENTION An object of the invention is an electronic pulse generator for operating at least one valve of an internal combustion engine.

Another object of the invention is the electronic pulse generator of the preceding object, which pulse generator operates at least two valves of the internal combustion engine.

Another object of the invention is a pulse generator for operating one or more valves of an internal combustion engine, the pulse generator opening the valve or valves at a predetermined angle of the crank shaft and holding the valve or valves opened while the crank shaft rotates through an angle that is independent of engine speed.

Briefly, the invention consists of means for generating at least one first and at least one second train of electric pulses in synchronism with the engine speed and having a keying ratio independent of engine speed, each first pulse train being for operation of a respective inlet valve, and each second pulse train being for operation of a respective outlet valve, the means for generating electric pulses including means for shifting, in degrees of crank shaft rotation, the first and second pulse trains with respect to each other independent of engine speed, the means for generating electric pulses further including an angle of rotation signal generator, a staircase waveform generator connected to the angle of rotation signal generator to receive as input the output thereof, and threshold switch means connected to the output of the staircase generator for controlling at least one inlet and one outlet valve.

In accordance with the invention, the pulses for operating the inlet valves and the pulses for operating the outlet valves can be made to overlap.

The control pulses fed to the pulse generator of the invention can be obtained from a distributor having a single switching deck, or from a magnetic or photoelectric pulse generator.

The-novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an embodiment of the invention;

FIGS. 2, 3 and 4 graphically explain certain aspects of the operation of the circuit shown in FIG. 1;

FIGS. 5 and 7 are block diagrams of two modifications of the embodiments shown in FIG, 1;

FIGS. 6, 9 and 10 graphically explain certain aspects of the operation of the embodiment shown in FIG. 5; and

FIG. 8 is a block diagram of a still further modification of the embodiment shown in FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With references to FIG. 1, there is shown a block dia-- gram of one embodiment of the pulse generator for the inlet valve and the outlet valve of one cylinder of an internal combustion engine. The embodiment is largely composed of digital circuit components. The angle of rotation signal generator 101 delivers a large number of pulses (1,000, for example) for each rotation of the crank shaft. The angle of rotation signal generator comprises a toothed wheel 102, the shaft 103 of which is connected by step down gearing to the crank shaft of the internal combustion engine so that the wheel 102 rotates at one-half of the speed of the crank shaft. The wheel 102 is made of a ferromagnetic material, the teeth of the wheel passing by the two ends of a core 106 of a coil 107. The teeth induce in the coil 107 alternating voltage pulses of which the frequency is proportional to the rpm of the toothed wheel 102. The core 106 is magnetized by connecting the coil 107 between the positive rail 122 and ground. Connected to the output of the generator 101 is a staircase waveform generator 100, the circuit of which will be described.

A cam 104 mounted on the shaft 103 closes a switch once every rotation of the crank shaft. The stationary contact of the switch 105 is connected by a differentiator to the zero position input 0 of a binary counter 112. The differentiator advantageously is an RC network composed of the capacitor 111 and the resistor 111a. A differentiator, composed of a capacitor and of the resistor 110a, connects the coil 107 to the counting input v of the binary counter 112.

Weighted summing resistors (only four, 113 to 116, being shown in FIG. 1) connect the outputs of the binary counter 112 to the inverting input of an operational amplifier 120, which acts as a summing amplifier. The inverting inputof the operational amplifier is also connected by a register 117 to the positive rail 1'22 and by a negative feedback resistor 121 to the output of the amplifier. The non-inverting input of the operational amplifier 120 is connected to the junction between the resistors l 18 and 119 that compose a voltage divider.

The summing resistors 113 to 116 and the resistor 117 compose the input voltage divider of the inverting input of the operational amplifier 120. The resistance value of the individual summing resistors is inversely proportional to the numerical value of the associated input. In other words, the resistor 116, which is associated with the number 1, has a resistance eight times greater than the resistor 113, which is associated with the number 8. The purpose of the resistor 117 is to put the output of the operational amplifier at negative voltage when the binary counter 112 is at zero.

Coupling resistors 127, 128, 129 and 130 connect the output of the operational amplifier 120 to the inverting inputs of four additional operational amplifiers 123,

which latter jumps in the positive direction, as shown 7 by curve 167, and opens the inlet valve. When the out- 124, 125 and 126. The positive feedback resistors 139,

140, 141, and 142 connect these operational amplifiers as threshold switches. These positive feedback resistors cause a small switching hysteresis, which is essential for the operation of the threshold switches. Input resistors, 131, 132, 133 and 134 connect the non-inverting inputs to the terminal 135, 136, 137 and 138. Correction voltages can be conducted to these terminals for the purpose of changing the moment at which the individual valves are opened or closed.

The outputs of the first two operational amplifiers 123, 124 are connected by respective RC differentiating networks 143, 143a and 144, 144a with the inputs of a first bistable trigger 147, which is connected to a switching amplifier 149 to control the inlet valve of a cylinder of the engine. In the same way, the outputs of the two operational amplifiers 125, 216 are connected by RC differentiating networks 145, 145a and 146, 146a to the inputs of a second bistable trigger 148, which operates the outlet valve through a further switching amplifier 150.

FIG. 2 shows the voltage-time relationship of the output voltages of the different stages of the circuit shown in FIG. 1. The curves 160 to 168 show respectively the output voltage. of the angle of rotation signal generator 101, the RC network 111 and 111a, the operational amplifier 120, the RC networks 143, 143a and 144, 144a and 145, 145a, 146, 1460, the first bistable trigger 147, and the second bistable trigger 168. The respective thresholds of the four threshold switches 123 to 126 are denoted by El, E2, E3, and E4. The curves 169 and 170 respectively show the stroke of the inlet valve and of the outlet valve, plotted against degrees of rotation KW of the crank shaft.

The operation of the second embodiment will now be described in connection with FIGS. 1 and 2. At a determined angle of the crank shaft, the switch 105 resets the binary counter 112 to zero. The binary counter then counts the individual output pulses of the coils 107. The larger the count, the smaller is the total resistance of the summing resistors 113 to 116, so that the input voltage of the inverting input of the operational amplifier 120 falls more and more. As shown by the curve 162 in FIG. 6, there appears at the output of the operational amplifier 120 an increasingly positive staircase voltage.

When the threshold E1 of the first threshold switch 123 is exceeded, the output voltage of this switch jumps in the negative direction. The RC network 143, 143a conducts a negative voltage peak 163 to the first input of the first bistable trigger 147, the output voltage of put voltage of the operational amplifier 120 exceeds the threshold voltage E2 of the second threshold switch 124, the RC network 144 conducts a negative voltage peak 164 to a second input of the first bistable trigger 147. As shown by the curve 167, this trigger changes states and closes the inlet valve. When the threshold voltages E3 or E4 are exceeded, the same sequence of events takes place with respect to the outlet valve, as shown by the curves 168 and 170.

FIG. 3 shows on enlarged scale the exact relationship between the curves 167 and 169; between the output voltage of the first bistable trigger 147 and the stroke executed by the inlet valve. FIG. 3 clearly shows that there is a delay time t, between the turning on of the switching amplifier 149 and the beginning of the stroke of the inlet valve. Likewise, there is a delay time between the turning off of the switching amplifier 149 and the end of the stroke of the inlet valve. These delay times are caused by magnetic valves that are in the hydraulic circuit of the control for the valves. The delay times t, and are independent of the rpm of the engine. To ensure that the beginning and end of the valve stroke are independent of engine rpm and that they are always associated with the same crank shaft angles, the output pulses of the first bistable trigger 147 must be shifted more and more with increasing rpm.

The circuits shown in FIGS. 5 and 7 are used to shift the pulses. The circuit shown in FIG. 5 contains-the same major units as the circuit of the second embodiment shown in FIG. 1; therefore, the same reference numerals are used in FIG. 5 as in FIG. 1.

With reference to FIG. 5, there are provided two switches and 108, which a cam 104 successively closes during one rotation of the crank shaft. An RC differentiating network 111, 111a connects the first switch 105 to the input of a first monostable trigger 203 and to the second input of a third bistable trigger 204. The second switch 108 is connected by a further RC differentiating network 201, 201a to the first input of the fourth bistable trigger 202 and to the first input of the third bistable trigger 204.

The output of the fourth bistable trigger 202 is connected to the zero position input 0 of the binary counter 112. The right plate of the capacitor and the output of the first monostable trigger 203 are connected to respective inputs of a first AND gate 205. The output of the first AND gate 205 is connected with one input each of two AND gates 206 and 207, the other inputs of which latter AND gates are connected to the respective outputs of the third bistable trigger 204. The outputs of the AND gates 206 and 207 are respectively connected to the forward counting input v and to the backward counting input r of a forward and backward counter 208. The output of the counter is connected to a decoder 209. The only output of the decoder and the second output of the third bistable trigger 204 are connected to respective inputs of a third AND gate 210, the output of which latter is connected to the zero position input 0 of the counter 208 and to the second input of the fourth bistable trigger 202.

A fifth AND gate 192 is connected between the output of the first bistable trigger 147 and the input of the first switching amplifier 149, and a sixth AND gate 193 is connected between the output of the second bistable trigger 148 and the input of the second switching amplifier 150. The second inputs of the two AND gates 192 and 193 are connected to the output of a second monostable trigger 191. An OR gate 190 connects the outputs of the two bistable triggers 147 and 148 to the input of the second monostable trigger 191.

FIG. 6 shows, in addition to the curves shown in FIG. 2, the following curves: curve 172 for the output of the first monostable trigger 203, curve 173 for the counting sequence of the counter 208 when counting forward, and curve 175 for the output voltage of the second monostable trigger 191.

FIG. 4 graphically shows the relationship between engine rpm and the shift as expressed in degrees of crank shaft rotation at for two different delay times t and where t is greater than t,. At the maximum engine rpm n,,,,,,,, the maximum shift angle a, is reached, which corresponds exactly to the included angle between the two switches 105 and 108.

FIGS. 9 and 10 show further pulse curves for explaining the operation of the circuits shown in FIG. 5. The reference numerals are unchanged from those used in FIGS. 4 and 6. In FIG. 6, t is less than t and in FIG. 10, t, is greater than t In both cases, the total pulse 174 is shifted an amount equal to the larger of the two delay times. In the first case, shown in FIG. 9, this means that the leading edge of the pulse is shifted too far forward, and the partial pulse 175 is removed from the leading edge, so that there results the valve control pulse 178. In the second case, shown in FIG. 10, the trailing edge of the pulse 174 is shifted too far forward, so that a pulse 1750 must be added to the trailing edge. There results the valve control pulse 1780.

The operation of the circuit shown in FIG. 5 will be explained in connection with FIG. 6. The first monostable trigger 203 produces a pulse having a length exactly equal to the larger of the two delay kinds, namely t When the first switch 105 is closed, this trigger changes to its unstable state and produces the output pulse 172, which prevents pulses from the angle of rotation signal generator 101 from being conducted by the first AND gate 205 to the forward and backward counter 208. At the same time that the first monostable trigger 203 is triggered, the first switch 105 triggers the third bistable trigger 204 to its first stable state. This latter trigger thereby cuts off the third AND gate 207 and opens the second AND gate 206.

After passage of the delay time t the first monostable trigger 203 returns to its stable state, thereby permitting the output pulses from the generator 101 to be conducted to the two AND gates 205 and 206. The forward and backward counter 208 counts forward (see curve 173), because pulses from the generator 101 are being conducted to the forward counting input v. The cam 104 continues to revolve and closes the second switch 108, the voltage pulse 171 appearing across the resistor 201a at the lowermost plate of the capacitor 201. The voltage pulse 171 changes the third bistable trigger 204 to its second stable state. Consequently, the second AND gate 206 is closed and the third AND gate 207 opened, the output pulses of the generator 101 now being conducted to the backward counting input r of the counter 208. The counter 208 now begins to count backward from the last binary number counted while counting forward. When the second switch 108 is closed, the fourth bistable trigger 202 is simultaneously returned to its first stable state. In doing so, it conducts a pulse to the zero position input 0 that resets the binary counter 112 to zero, as shown by curve 162.

If the counter 208 is at the binary number zero, and if at the same time the third bistable trigger 204 is in its second stable state, a signal conducted by the fourth AND gate 210 returns the fourth bistable trigger 202 to its second stable state, thereby freeing the binary counter 112. The output voltage of the operational amplifier now rises in the manner of a staircase, as shown by curve 162, and as previously explained in connection with FIG. 2.

It will now be assumed that the generator 101 delivers 20 pulses when the crank shaft turns through an angle equal to the angle of separation between the two switches 105 and 108. These 20 pulses are delivered between the two voltage peaks 161 and 171. At a very low rpm, the output pulse 172 of the first monostable trigger 203 covers two such pulses 160, so that the counter 208 counts to 18 and then is caused to count in the reverse direction by the second voltage peak 171. At this low engine rpm, the staircase voltage 162 begins to rise 18 pulses 160 after the second voltage peak 171.

At a very high engine rpm, the output pulse 72 covers the first 18 pulses 160, for example, so that the counter 208 only counts up to 2 and then is reversed to count backward. The staircase voltage 162 begins in this instance two pulses after the second voltage peak 171. The length of the output pulses 172 of the first monostable trigger 203 is exactly as long as the larger of the two delay times t and t and therefore, at the maximum engine rpm n (see FIG. 4), precisely fills the time between the two voltage peaks 161 and 171.

Consequently, at the engine rpm n the staircase voltage 162 is shifted the most. With decreasing engine rpm, the beginning of the staircase voltage 162 is shifted to later and later times. The circuit described shifts both the leading edge and the trailing edge of the output pulse 174 of the first bistable trigger 147 an amount equal to the larger of the two delay times 1 and t It has been assumed that is greater than t,. The second monostable trigger 191 adjusts for a difference between the two delay times t, and t Thelength of the output pulse 175 of the second monostable trigger 191 is exactly equal to the difference between the two delay times t minus t,. The second monostable trigger .191 is triggered just then when the threshold voltage E1 of the first threshold switch 123 is exceeded, causing the first bistable trigger 147 to change to its second stable state, as shown by curve 174. As long as the second monostable trigger 191 is in its unstable state, the fifth AND gate 192 does not conduct, so that the switching amplifier 149 is not turned on until the output pulse 175 of the second monostable trigger 191 has occurred. The first switching amplifier 149 therefore has the pulse 178. The leading edge of the pulse 178 is shifted a smaller amount. The fact that the delay time t, is smaller than the delay time has been taken into account. The second monostable trigget 191 influences the inlet valve of the internal combustion engine-through the fifth AND gate 192, and influences the outlet valve through the sixth AND gate 193.

If the first delay time t, is greater than the second delay time t,, the circuit shown in FIG. 5 must be suitably altered. It is only necessary to replace the two AND gates 192 and 193 by OR gates. There results the pulses shown in FIG. 10. The switching amplifier 149 then opens the associated inlet valve when either the bistable trigger 147 or the monostable trigger 191 delivers the positive output signal. The monostable trigger 191 is so driven that it is triggered to its unstable state by the leading edge of the pulse from the bistable trigger 147, so that the output pulse of the monostable trigger 191 is added to the output pulse of the bistable trigger 147.

In some instances, it may be essential that the tw valves are simultaneously energized by the switching amplifiers 149 and 150, so that both valves are simultaneously opened. In this case, the monostable trigger 191 must be replaced by two separate monostable triggers, one for the inlet valve and one for the outlet valve. The OR gate 190 can then be omitted.

The circuit shown in FIG. is composed entirely of digital circuit components. In accordance with the invention, the binary counting sequence 173 (see FIG. 6) can also be obtained with an analog circuit, not with binary counting but with triangle voltages.

The circut for carrying out this modification of the invention is shown in FIG. 7. The two inputs of a bistable trigger 204 are respectively connected to the switch 105 and the switch 108. The'first output of the trigger 204 is connected to the input of a monostable trigger 211, and the second output is connected to a first input of an AND gate 212. The output of the monostable trigger 211 is connected to the second input of the AND gate 212 and with the control input of a first constant current source 213. The first constant current source is connected between the positive rail 122 and the input plate of a storage capacitor 215. A second constant current source 214 is connected between this plate of the capacitor-215 and ground. The output of the AND gate 212 is connected to the control input of the second constant current source 214. The voltage across the storage capacitor 215 controls a threshold switch 216. a

The operation of the delay circuit shown in FIG. 7 is somewhat different from that of the delay circuit shown in FIG. 5. When the first switch 105 closes, the monostable trigger 211 is changed to its unstable state. During the length of time of the output pulse of the monostable trigger 211, both constant current sources 213 and 214 are cut off. When the monostable trigger 211 returns to its stable state, the first constant current source 213 becomes conductive and charges the storage capacitor 215. When the second switch 108 closes, the bistable trigger 204 returns to its other state and makes the constant current source 214 conductive. The AND gate 212 is provided to ensure that the storage capacitor 215 can be discharged only after occurrence of the pulse from the monostable trigger. The amounts of current conducted by the two constant current sources 213 and 214 are so adjusted that the capacitor 215 is charged and discharged with currents of the same strength. The magnitude of the charging voltage across the capacitor 215 depends on the length of time between the return of the monostable trigger 21 1 and the closing of the second switch 108. This charging voltage is therefore the smaller the greater the engine rpm. The variation of the voltage with time is similar to that shown by curve 173 in FIG. 6. The threshold switch 216 is operated w'henthe voltage across the storage capacitor 215 is again zero.

FIG. 8 shows how the embodiment shown in FIG. 5 must be expanded for a plurality of cylinders, in this case for a four cylinder internal combustion engine.

The circuit shown in FIG. 8 includes a first binary counter 220, the output of which is connected to a decoder 221. The counting input v is connected to the output of the angle of rotation signal generator 101. A first OR gate 225 connects the input terminal 224 to the zero position input 0 of the counter 220. The input terminal 224 is connected to the output of the first switching amplifier 149, which operates the inlet valve of the first cylinder. The only output of the decoder 221 is connected both to the first OR gate 225 and the forward counting input v of a ring counter 228. The output of the ring counter 228 is connected to a decoder 229, the first output of which is unconnected. The second, the third, and the fourth outputs are respectively connected to the first inputs of a bistable trigger 232, 233 and 234. These bistable triggers control switching amplifiers 235, 236 and 237. These switching amplifiers operate the inlet valves of the second, the third, and the fourth cylinders of the internal combustion engine.

An inverting stage 226 and an OR gate 227 connect the input terminal 224 to the zero position input 0 of a second binary counter 222. The forward counting input v of the second binary counter is connected to the output of the angle of rotation signal generator. Connected to the output of the second binary counter is the decoder 233, the single output of which is connected with a second input of the second OR gate 227 and with the forward counting input v of a second ring counter 230.

Both ring counters 228 and 230 have synchronizing inputs s, which are connected to the input terminal 224. The outputs of the second ring counter 230 are connected to a decoder 231, one output of which latter remains unconnected, the second, third, and fourth outputs of which are connected to respective second inputs of the bistable triggers 232, 233, and 234.

With the circuit shown in FIG. 8, the angle of the crank shaft is measured by the number of output pulses of the angle of rotation signal generator 101. Assume,

for example, that in a four cylinder engine the valves of successive cylinders are to be opened with an angular spacing of of crank shaft rotation. If the generator 101 produces, for example, 1,000 pulses for every complete rotation of the crank shaft, then the inlet valve of the second cylinder will be operated exactly 250 pulses after the operation of the inlet valve of the first cylinder. The leading edge of the control pulse 178 is conducted by the first OR gate 225 to reset the first binary counter 220 to zero, when the first inlet valve is operated. At the same time, signals conducted to the two synchronizing inputs s reset the ring counters 228 and 230 to one. After 250 pulses, the output of the decoder 221 conducts a counting pulse to the ring counter 228, so that an output signal is on the second output lead of the decoder 229. In this way, the second inlet valve is operated. The second inlet valve is closed through the switching amplifier 225 when the second output of the decoder 231 delivers -a signal, thereby changing the states of the trigger 232. This is the case when 250 pulses after the trailing edge of the pulse 178 have been delivered. The trailing edge of the pulse 178 is conducted by the inverter 226 and the OR gate 227 to the second binary counter 222, and resets the latter to zero.

The counters 220 and 228 are associated with the leadingedge of the control pulse, and the counters 222 and 230 are associated with the trailing edge of the control pulse. The third valve is operated at 250 pulses after the second valve, and the fourth valve isoperated after a further 250 pulses.

A circuit exactly as that shown in FIG. 8 is also required for the outlet valves of the cylinder. All in all, this embodiment of the invention is appreciably simpler than the embodiment shown in-FIG. 4 in commonly assigned U.S. Pat. application Ser. No. 136,322, filed on Apr. 22, 1971 in the name of Wolf Wessel. Neither embodiment is limited in application to controlling the valves of an internal combustion engine. It can also be used as a pulse generator for controlling the fuel injection arrangement or the ignition of the engine. Both the time when the fuel is injected and when the mixture is ignited must be altered in dependence on the engine operating parameters. Control signals that reflect these parameters can be conducted by way of the input terminal 32 in the embodiment shown in FIG. 2 of the aforesaid patent application, or to the input terminals 135, 136, 137, and 138 of the embodiment shown in FIG. 5 of this invention.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.

While the invention has been illustrated and described as embodied in a pulse generator for controlling the valves of an internal combustion engine, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. A pulse generator for operating the electrohydraulie or electropneumatic control for the inlet and outlet valves of an internal combustion engine, comprising, in combination, means for generating at least one first and at least one second train of electric pulses in synchronism with the engine speed and having a keying ratio independent of engine speed, each said first pulse train being for operation of a respective inlet valve, and each second pulse train being for operation of a respective outlet valve, said means for generating electric pulses including means for shifting, in degrees of crank shaft rotation, the first and second pulse trains with respect to each other independent of engine speed, said means for generating electric pulses further including an angle of rotation signal generator, a staircase waveform generator connected to said angle of rotation signal generator to receive as input the output thereof, and threshold switch means connected to the output of said staircase generator for controlling at least one inlet and one outlet valve.

2. The pulse generator as defined in claim 1, wherein said angle of rotation signal generator includes toothed wheel means mounted to rotate synchronously with the engine crank shaft, the teeth of said wheel means being ferromagnetic, and coil means connected to current and cooperating with the teeth of said wheel means so as to have induced in said coil means electric pulses when said wheel means rotates.

3. The pulse generator as defined in claim 1, further including switch means connected to said staircase generator for resetting the latter to zero, and means cooperating with the engine crank shaft and with said switch means to close the latter once every rotation of the crank shaft.

4. The pulse generator as defined in claim 1, wherein said staircase generator includes a binary counter having a plurality of outputs, a resistor of weighted value connected to a respective output, and amplifier means connected to the weighted resistors to receive the voltages thereon as input.

5. The pulse generator as defined in claim 4, wherein said amplifier means is an operational amplifier.

6. The pulse generator as defined in claim 1, wherein said threshold switch means includes at least two pairs of threshold switches, each switch of a pair having an electric output, and further including a respective bistable trigger connected to each pair of threshold switches to receive as input the output thereof for controlling a valve of the engine.

7. The pulse generator as defined in claim 1, including first circuit means for shifting both the leading edge and the trailing edge, independent of the engine speed, of the first and second trains of electric pulses so as to adjust for the delay times t and T where t is the turn on delay time and t the turn off delay time of the controls for the inlet and outlet valves.

8. The pulse generator as defined in claim 7, wherein said first circuit means shifts both pulse edges an amount equal to the larger of said delay times t and t 9. The pulse generator as defined in claim 8, wherein said first circuit means shortens a pulse at the leading edge by an amount equal to 1 minus t when t; is greater than l 10. The pulse generator as defined in claim 8, wherein said first circuit means lengthens a pulse at the trailing edge by an amount equal to t minus t when t is greater than 1 l l. The pulse generator as defined in claim 7, including first and second switch means for operating said first circuit means, and means cooperating with the engine crank shaft and with said first and second switch means for successively closing the latter once during each rotation of the crank shaft.

12. The pulse generator as defined in claim 11, wherein said first circuit means includes monostable trigger means and first and second bistable trigger means, said first and second bistable trigger means each having first and second inputs, said first switch means being connected to the input of said monostable trigger means and to the second input of the first bistable trigger means, said second switch means being connected to the first inputs of said first and second bistable trigger means.

13. The pulse generator as defined in claim 12, including respective differentiating means connected to each of said first and second switch means.

14. The pulse generator as defined in claim 13, wherein each said differentiating means is an RC network.

15. The pulse generator as defined in claim 12, wherein said first circuit means includes a forward and backward counter, vsaid counter having a forward counting input and a vbackward counting input, a decoder connected to receive as input the output of said counter, said decoder having an output, and AND gate means connecting the two inputs of said counter to the output of said rnonostable trigger means, and to the output of said angle of rotation signal generator.

16. The pulse generator as defined in claim 15, wherein said AND gate means includes first, second, and third AND gates, the outputs of said second and third AND gates being connected respectively to said forward counting input and said backward counting input, the output of said first AND gate being connected to one input of each of said second and third AND gates, one input of said first AND gate being connected to the output of said rnonostable trigger means, and the other input of said first AND gate being connected to the output of said angle of rotation signal generator.

17. The pulse generator as defined in claim 16, wherein said first bistable trigger means has first and second outputs, and one input of each of said second and third AND gates is connected to respective ones of the two outputs of said first bistable trigger means.

18. The pulse generator as defined in claim 17, further including an AND gate connecting the output of said decoder and one output of said first bistable trigger means to the second input of said second bistable trigger means.

19. The pulse generator as defined in claim 7, further including second circuit means for adjusting for the different said delay times t, and t, of the controls for the inlet and outlet valves.

20. The pulse generator as defined in claim 6, further including an OR gate connected to receive as input the output of each said bistable trigger; a rnonostable trigger connected to receive as input the output of said OR gate; a first AND gate, said gate having first and second inputs respectively connected to the output of one said bistable trigger and to the output of said rnonostable trigger; a second AND gate, said gate having first and second inputs respectively connected to the output of another said bistable trigger and to the output of said rnonostable trigger; and first and second switching amplifiers for respective valves of the engine, said switching amplifiers being connected to receive as input the output of respective ones of the first and second AND gates.

21. The pulse generator as defined in claim 20, further including electronic counter means for obtaining from the control pulses for the first cylinder of the engine the control pulses for the remaining cylinders of the engine, said counter means being connected to receive as input the output of said angle of rotation signal generator and the output of said first and second switching amplifiers.

22. The pulse generator as defined in claim 21, including a first binary counter, a first decoder, a first ring counter, and a second decoder, all connected in series; a second binary counter, a third decoder, a second ring counter, and a fourth decoder, all connected in series.

23. The pulse generator as defined in claim 22, wherein the binary counters are forward and backward counters, said binary counters having each a forward counting input, said forward counting input of each said binary counter being connected to the output of said angle of rotation signal generator.

24. The pulse generator as defined in claim 23, wherein each ring counter has a synchronizing input and each binary counter has a zero position input, said synchronizing input of each ring counter being connected directly to the output of said first switching amplifier, and further including a respective AND gate connecting each said zero position input to the output of said first switching amplifier.

25. The pulse generator as defined in claim 24, further including bistable trigger means; switching amplifier means connected to receive as input the output of said bistable trigger means for controlling further valves of the engine, and wherein the output of each of said second and fourth decoders is connected to the input of said bistable trigger means.

It l l 

1. A pulse generator for operating the electrohydraulic or electropneumatic control for the inlet and outlet valves of an internal combustion engine, comprisinG, in combination, means for generating at least one first and at least one second train of electric pulses in synchronism with the engine speed and having a keying ratio independent of engine speed, each said first pulse train being for operation of a respective inlet valve, and each second pulse train being for operation of a respective outlet valve, said means for generating electric pulses including means for shifting, in degrees of crank shaft rotation, the first and second pulse trains with respect to each other independent of engine speed, said means for generating electric pulses further including an angle of rotation signal generator, a staircase waveform generator connected to said angle of rotation signal generator to receive as input the output thereof, and threshold switch means connected to the output of said staircase generator for controlling at least one inlet and one outlet valve.
 2. The pulse generator as defined in claim 1, wherein said angle of rotation signal generator includes toothed wheel means mounted to rotate synchronously with the engine crank shaft, the teeth of said wheel means being ferromagnetic, and coil means connected to current and cooperating with the teeth of said wheel means so as to have induced in said coil means electric pulses when said wheel means rotates.
 3. The pulse generator as defined in claim 1, further including switch means connected to said staircase generator for resetting the latter to zero, and means cooperating with the engine crank shaft and with said switch means to close the latter once every rotation of the crank shaft.
 4. The pulse generator as defined in claim 1, wherein said staircase generator includes a binary counter having a plurality of outputs, a resistor of weighted value connected to a respective output, and amplifier means connected to the weighted resistors to receive the voltages thereon as input.
 5. The pulse generator as defined in claim 4, wherein said amplifier means is an operational amplifier.
 6. The pulse generator as defined in claim 1, wherein said threshold switch means includes at least two pairs of threshold switches, each switch of a pair having an electric output, and further including a respective bistable trigger connected to each pair of threshold switches to receive as input the output thereof for controlling a valve of the engine.
 7. The pulse generator as defined in claim 1, including first circuit means for shifting both the leading edge and the trailing edge, independent of the engine speed, of the first and second trains of electric pulses so as to adjust for the delay times t1 and T2, where t1 is the turn on delay time and t2 the turn off delay time of the controls for the inlet and outlet valves.
 8. The pulse generator as defined in claim 7, wherein said first circuit means shifts both pulse edges an amount equal to the larger of said delay times t1 and t2.
 9. The pulse generator as defined in claim 8, wherein said first circuit means shortens a pulse at the leading edge by an amount equal to t2 minus t1 when t2 is greater than t1.
 10. The pulse generator as defined in claim 8, wherein said first circuit means lengthens a pulse at the trailing edge by an amount equal to t1 minus t2, when t1 is greater than t2.
 11. The pulse generator as defined in claim 7, including first and second switch means for operating said first circuit means, and means cooperating with the engine crank shaft and with said first and second switch means for successively closing the latter once during each rotation of the crank shaft.
 12. The pulse generator as defined in claim 11, wherein said first circuit means includes monostable trigger means and first and second bistable trigger means, said first and second bistable trigger means each having first and second inputs, said first switch means being connecteD to the input of said monostable trigger means and to the second input of the first bistable trigger means, said second switch means being connected to the first inputs of said first and second bistable trigger means.
 13. The pulse generator as defined in claim 12, including respective differentiating means connected to each of said first and second switch means.
 14. The pulse generator as defined in claim 13, wherein each said differentiating means is an RC network.
 15. The pulse generator as defined in claim 12, wherein said first circuit means includes a forward and backward counter, said counter having a forward counting input and a backward counting input, a decoder connected to receive as input the output of said counter, said decoder having an output, and AND gate means connecting the two inputs of said counter to the output of said monostable trigger means, and to the output of said angle of rotation signal generator.
 16. The pulse generator as defined in claim 15, wherein said AND gate means includes first, second, and third AND gates, the outputs of said second and third AND gates being connected respectively to said forward counting input and said backward counting input, the output of said first AND gate being connected to one input of each of said second and third AND gates, one input of said first AND gate being connected to the output of said monostable trigger means, and the other input of said first AND gate being connected to the output of said angle of rotation signal generator.
 17. The pulse generator as defined in claim 16, wherein said first bistable trigger means has first and second outputs, and one input of each of said second and third AND gates is connected to respective ones of the two outputs of said first bistable trigger means.
 18. The pulse generator as defined in claim 17, further including an AND gate connecting the output of said decoder and one output of said first bistable trigger means to the second input of said second bistable trigger means.
 19. The pulse generator as defined in claim 7, further including second circuit means for adjusting for the different said delay times t1 and t2 of the controls for the inlet and outlet valves.
 20. The pulse generator as defined in claim 6, further including an OR gate connected to receive as input the output of each said bistable trigger; a monostable trigger connected to receive as input the output of said OR gate; a first AND gate, said gate having first and second inputs respectively connected to the output of one said bistable trigger and to the output of said monostable trigger; a second AND gate, said gate having first and second inputs respectively connected to the output of another said bistable trigger and to the output of said monostable trigger; and first and second switching amplifiers for respective valves of the engine, said switching amplifiers being connected to receive as input the output of respective ones of the first and second AND gates.
 21. The pulse generator as defined in claim 20, further including electronic counter means for obtaining from the control pulses for the first cylinder of the engine the control pulses for the remaining cylinders of the engine, said counter means being connected to receive as input the output of said angle of rotation signal generator and the output of said first and second switching amplifiers.
 22. The pulse generator as defined in claim 21, including a first binary counter, a first decoder, a first ring counter, and a second decoder, all connected in series; a second binary counter, a third decoder, a second ring counter, and a fourth decoder, all connected in series.
 23. The pulse generator as defined in claim 22, wherein the binary counters are forward and backward counters, said binary counters having each a forward counting input, said forward counting input of each said binary counter being connected to the output of said angle of rotatioN signal generator.
 24. The pulse generator as defined in claim 23, wherein each ring counter has a synchronizing input and each binary counter has a zero position input, said synchronizing input of each ring counter being connected directly to the output of said first switching amplifier, and further including a respective AND gate connecting each said zero position input to the output of said first switching amplifier.
 25. The pulse generator as defined in claim 24, further including bistable trigger means; switching amplifier means connected to receive as input the output of said bistable trigger means for controlling further valves of the engine, and wherein the output of each of said second and fourth decoders is connected to the input of said bistable trigger means. 